Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R48: Drops IFocus
|
Hide Abstracts |
Sponsoring Units: DFD GSOFT GSNP Chair: Daniel Harris, Brown University Room: BCEC 251 |
Thursday, March 7, 2019 8:00AM - 8:12AM |
R48.00001: Marangoni convection in an evaporating sessile droplet depending on the substrate temperature. Lev Barash, Alexandra Gavrilina We investigate numerically quasi-steady internal flows in an axially symmetrical evaporating sessile droplet of capillary size. The hydrodynamics of an evaporating sessile drop and effects of the thermal conduction in the droplet and substrate have been taken into account jointly. The equations have been solved by finite element method using ANSYS Fluent. Temperature distributions and the corresponding vortex structures in evaporating sessile droplets are obtained. The phase diagrams containing information on the number and orientation of the vortices depending on the ratio of substrate to fluid thermal conductivities and the contact angle, are presented and analyzed for different values of parameters. Depending on the substrate temperature, we obtain both axisymmetric and asymmetric fluid flow patterns. |
Thursday, March 7, 2019 8:12AM - 8:24AM |
R48.00002: Spreading and contracting three-component droplets for cleaning high energy surfaces Dieter Baumgartner, Shayandev Sinha, Nate J. Cira Marangoni flows are a well established mechanism for inducing droplet spreading and contraction. In this work, we study the behavior of a three-component mixture (ethanol, water, and propylene glycol) on high energy surfaces. Evaporation of the ethanol (most volatile, lowest surface tension) results in a higher surface tension around the perimeter of the droplet and rapid spreading. After ethanol evaporation, water evaporation (next most volatile component, highest surface tension) from the perimeter induces a reversal in the direction of Marangoni flow and droplet contraction. We investigate this ternary parameter space to unravel the interplay of Marangoni flow, capillary flow, and evaporation. The self-expansion and contraction of these droplets make them suitable for cleaning even high energy surfaces. |
Thursday, March 7, 2019 8:24AM - 8:36AM |
R48.00003: Binary Droplets Walking With Their Feet. Jehan Charlier, Alexey Rednikov, Sam Dehaeck, Pierre Colinet, Denis Terwagne
|
Thursday, March 7, 2019 8:36AM - 8:48AM |
R48.00004: Tears of Wine Prerana Rathore, Chenxian Xu, Vivek Sharma `Tears of wine' refer to the rows of wine-drops that spontaneously emerge within a glass of strong wine. Evaporation-driven Marangoni flows near the meniscus of water-alcohol mixtures drive liquid upward forming a thin liquid film, and a rim or ridge forms near the moving contact line. Eventually, the rim undergoes an instability forming drops, that roll back into bulk reservoir forming so-called tears or legs of wine. Most studies in literature argue the evaporation of more volatile, lower surface tension component (alcohol) results in a concentration-dependent surface tension gradient that drives the climbing flow within the thin film. Though it is well-known that evaporative cooling can create temperature gradients that could provide an additional contribution to the climbing flows, the role of thermocapillary flows is less well-understood. Furthermore, the patterns, flows and instabilities that occur near the rim, and determine the size and periodicity of tears, are not well-studied. Using experiments and theory, we visualize and analyze the formation and growth of tears of wine. The sliding drops, released from the rim towards the bulk reservoir, show oscillations and a cascade of fascinating flows that are analyzed for the first time. |
Thursday, March 7, 2019 8:48AM - 9:00AM |
R48.00005: On the role of internal geometry on droplet breakup in premix membrane emulsification Soeren Brandt, Amar Gharial, C. Nadir Kaplan, Joanna Aizenberg Although our bodies are mostly made of water, many of the materials we eat, wear on our skin, or use to treat diseases are insoluble in water. To overcome this challenge, we make emulsions by dispersing these materials as small oil droplets in water, which can then be used for foods, cosmetics, and pharmaceuticals. Current methods to make emulsions are either energy inefficient or produce excessive heat and are therefore unsuitable for more delicate materials. In contrast, premix membrane emulsification can be used with highly sensitive materials and is energy efficient. Various types of membranes have been used to demonstrate the applicability of premix emulsification, but we currently do not understand the role of the internal membrane geometry on droplet breakup. We designed microfluidic models to mimic common structures found in these membranes to explore the forces that lead to breakup in premix emulsification. We found a unique mechanism that causes droplet breakup in membranes with corrugated pores. In these membranes, breakup is determined by a competition of capillary forces and restricted transport across narrow constrictions along the pores. By exploiting this competition, we can potentially tailor membranes for specific applications to produce low-cost emulsions. |
Thursday, March 7, 2019 9:00AM - 9:12AM |
R48.00006: Instabilities of Polygonal Rings of Bouncing Droplets Miles Couchman, John WM Bush Millimetric droplets bouncing on the surface of a vibrating fluid bath may interact through their shared wavefield to form bound states. In this talk, we present the results of an experimental and theoretical investigation of the stability of polygonal droplet rings. As the vibrational acceleration of the bath is increased progressively, initially stationary rings destabilize into a variety of dynamical states, often characterized by radial and azimuthal oscillations as well as transitions to more complex geometrical structures. The observed behavior is dependent on the number, size and initial separation of the drops in the ring. Extensions to the stability of droplet lattices and connections with vortex arrays in superfluid helium and Bose Einstein condensates are discussed. |
Thursday, March 7, 2019 9:12AM - 9:24AM |
R48.00007: Axisymmetric Lattice Boltzmann Model of Droplet Impact on Curved Surfaces Hussein Dalgamoni, Xin Yong The fast rebound of droplets from surfaces is essential in many engineering applications, as it preserves the dryness of a surface and prevents corrosion. Other applications include anti-icing, self-cleaning and anti-contaminated surfaces. During the impact of a droplet on curved surface, the morphology of the droplet evolves differently compared to that on flat surface. For instance, the central lamella of the droplet exhibits complex variation in thickness during impact. This complex morphological change may result in a reduction in the contact time. Using axisymmetric lattice Boltzmann model, the dynamic behavior of droplet impact on hydrophobic curved surfaces will be studied. The study will reveal the dynamic evolution inside and outside the lamella during impact, mainly, the velocity vectors field and the morphological progress of the droplet. The contact time between the droplet and the solid surface before total rebound will be measured for various impact scenarios i.e. different equilibrium contact angles and different surface curvature, which will assist in the optimization of contact time in related applications. |
Thursday, March 7, 2019 9:24AM - 9:36AM |
R48.00008: Drop Squeezing through Arbitrarily Shaped Obstacles Jacob Gissinger, Alexander Z Zinchenko, Robert Davis Emulsions are encountered in a variety of environments, such as multiphase flow through fibrous materials, packed beds with complex pellet shapes, and tortuous subsurface settings. Efforts to numerically model droplet-resolved, nonwetting emulsions in complex environments have been stymied, chiefly due to the extremely close approach of fluid-fluid interfaces to solid surfaces. A multimesh desingularization technique is introduced to model the flow of tight-squeezing drops through arbitrary Lyapunov surfaces, i.e., smooth solid obstacles, using a boundary-integral formulation. The method utilizes a hierarchy of embedded mesh resolutions to approximate analytical single- and double-layer contributions from solid particles, for use by the high-order singularity subtraction scheme introduced by Zinchenko and Davis (2006). We present a fully three-dimensional study of drop squeezing through parallel cylindrical particles. Squeezing behavior through a fibrous material using this model is characterized with respect to capillary number, viscosity ratio and droplet size. The critical capillary number, below which trapping occurs, is found to lie between those of two-sphere and three-sphere constrictions. |
Thursday, March 7, 2019 9:36AM - 9:48AM |
R48.00009: A versatile 3D-printed droplet-on-demand generator Nikolay P Ionkin, Daniel M Harris There is a rapid and persistent growth in the study of dynamical behavior of droplets, however, the precise generation of these droplets over a range of sizes can be challenging. A versatile 3D-printed droplet-on-demand generator is presented for laboratory use. The design is modeled off of an existing design [Harris et al., Experiments in Fluids, 56:83 (2015)] but is tested with an extended range of working fluids and the manufacturing process is greatly simplified by 3D-printing the principal components. The present device is tested with deionized water and water-glycerol mixtures, and was reliably able to produce single droplets-on-demand of diameters 0.65-1.32 mm with an overall variability of less than 1%. Tips for fabrication, operation, and maintenance as well as potential applications will be discussed throughout. |
Thursday, March 7, 2019 9:48AM - 10:00AM |
R48.00010: Axisymmetric Ellipsoidal Droplet Impact on a Horizontal Solid Surface Xuan Zhang, Xin Liu, Xiaomin Wu, Jingchun Min Droplet impact process on a solid surface exists in fields such as coating chemistry, inkjet printing, aerospace, etc. In many cases, the initial shape before a droplet impacts on the surface will be effected by the surroundings including flow, gravity and electric field and so on. Thus, a droplet with irregular initial shape will have a quite different impact process from a spherical droplet. In this work, the impact processes of spherical droplets are first simulated using VOF multiphase model coupled with Kistler's dynamic contact angle model, which is verified by the results in our experiment and reference. Then, simulations are conducted on the impact processes of axisymmetric ellipsoidal droplets with different aspect ratios (0.5~2.0) under serials of contact angle (30°~150°) and We number (10~90). It is found that the maximum spreading factor and its corresponding time increases with increases of We number and aspect ratio and decrease of contact angle. Based on an approximate theoretical analysis, an correlation between the maximum spreading factor and We number, contact angle and aspect ratio is proposed, aimed to improve the understanding of the mechanism of droplet impact. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700